The present invention relates to a method of setting and a method of retrieving a device in a flow pipe. More particularly, the present invention relates to a method for setting into an undersea flow pipe a device which is provided with an opening to allow the flow to pass therethrough.
Pipes are widely used in the industry to transport diverse kinds of fluids. Such fluids may comprise a single constituent or multiple constituents, they may comprise a single phase or multiple phases, and they may be highly compressible or they may be almost not compressible. Such pipes may be provided with varying internal diameters and configurations. In the oil industry the pipes, or flow pipes, as they are usually referred to, are used to promote the flow of fluids from oil producing wells to gathering centers, where the fluids are processed.
When an undersea oil field is commercially exploited, it is necessary for the production from the oil producing wells to flow through pipes to a production unit located at the surface. An undersea flow pipe in usually connected at one end to an oil producing well and lies down on the sea bed but is connected at its other end to an undersea flow riser, which carries the fluids to the production unit at the surface.
Situations may occur in which it is necessary to insert a hollow device into the undersea flow pipe, in a certain location. Such device can for example be a body, externally shaped to match the inside of a portion of the undersea flow pipe where it is to be located with an orifice of any shape extending longitudinally therethrough so as to provoke a constriction in the flow.
The object of the insertion of such device into the undersea flow pipe may be, for example, to introduce a constriction in the flow to control the features of this flow, or to introduce an element intended to be used in flow rate measuring operations. In the oil industry situations occur in which there is the need to control the phenomenon known as severe slugging, which may occur in production systems provided with descending flow pipes followed by flow risers.
The severe slugging phenomenon is characterized by intense oscillations in the pressure and flow rate levels occurring in a multiphase flow having a gaseous phase. The severe slugging phenomenon causes disturbances to the undersea production activities, which can seriously impair or even shut the oil production down.
GB 2 341 695, commonly owned by the applicants of the present patent application, discloses a device used to control the severe slugging phenomenon. A hollow device, preferably a venturi, is installed into a descending undersea flow pipe relatively close to the junction to a flow riser.
The design of new undersea flow pipe may anticipate the need of such hollow device, which can be installed during the deployment of the undersea flow pipe. In existing undersea flow pipes where access to the interior of the undersea flow pipe is easy and the oil production flow can be interrupted, the hollow device can be installed after cutting the undersea flow pipe, the integrity of the undersea flow pipe being reinstated by using any of the known pipe assembling techniques, e.g., welding.
However, besides causing ceasing of profits, shutting down of the production can cause many operational problems, especially in undersea flow pipe under the effects of low temperatures of the sea bed. Many of these undersea flow pipes are located at great depth of sea, hindering the access of divers. A cutting operation in such undersea flow pipe would be very difficult to implement, as it involves the retrieval of the undersea flow pipe from the seabed, or carrying out the operation using a remote operated vehicle, both being extremely expensive, time consuming and complex operations.
Thus, there has been a need to provide a way to install a hollow device as described in GB 2 341 695 in undersea flow pipe without causing the above drawbacks. The present invention propose the use of polymeric foam blocks to set the hollow device in its operational position.
Polymeric foam blocks, usually cylindrical in shape, are widely used to clean the interior of pipes. Generally, one or more polymeric foam blocks are inserted into a pipe which is to be cleaned. Such polymeric foam blocks are usually driven throughout the pipe by the flow of fluids which may or may not be the same kind of fluid which is already flowing in the flow pipe.
In the oil industry such polymeric foam blocks are known as foam pigs, and are widely used, especially for cleaning the inside of gas pipes and oil pipes. EP 0 581 616 A1, of Aug. 2, 1993, commonly owned by the applicants of the present patent application, discloses a process which makes use of a pig to remove deposited liquids from the interior of a pipe.
The foam pigs are usually formed from polyurethane foam, though other material having flexible features may also be used. An important feature of the foam pigs is its extreme ability to adapt itself to changes in the inside diameter of a pipe. Even in pipes having severe constrictions located at certain points, the foam pig proves to be able to pass therethrough.
Thus, having the need to install a hollow device such as the disclosed in GB 2 341 695 in an existing undersea flow pipe, the use of flexible foam pigs is preferred for installing the hollow device in its operational position, as will be seen hereafter.
The present invention relates to a method of setting a hollow device into a pipeline and a method of retrieving it.
In a first aspect the present invention relates to a method of setting a hollow device into an undersea flow pipe having a flow of fluids flowing in it, the method comprising:
inserting at least one stop means into a position where said hollow device is to operate;
first inserting said hollow device ahead of a driving means into an end of said flow pipe located upstream of a point where said hollow device should operate;
allowing said driving means to be urged by said flow flowing in said flow pipe, thereby displacing said hollow device along said flow pipe;
allowing said at least one stop means to halt the displacement of said hollow device, thereby setting said hollow device into its operating position; and
allowing said driving means to pass through a passage into said hollow device, urged by a pressure exerted by said flow.
Preferably said driving means is a flexible pig.
In a second aspect the present invention relates to a method of retrieving a hollow device located in a flow pipe having a flow of fluids flowing in it by at least one stop means provided in said flow pipe, the method comprising:
removing said at least one stop means from the interior of said flow pipe;
inserting a driving means into a first end of said flow pipe located upstream of a point where said hollow device operates;
allowing said driving means to be urged by said flow flowing in said flow pipe; and
allowing said driving means to contact said hollow device, thereby displacing it towards a second end of said flow pipe where said driving means and said hollow device can both be retrieved.
Preferably said driving means is a pig.
A third aspect of the invention provides a stop means for halting displacement of a hollow device in an undersea pipe flow, said stop means comprising:
a first flange of a flanged spool able to be welded over an orifice drilled in an outer wall of a said flow pipe at a point where said hollow device will operate, with an internal passage of said spool substantially in registration with said orifice;
a bonnet of a gate valve connected to a second flange of said flanged spool, said bonnet being provided with a stem and with a gate connected to a lower end of said stem, said bonnet having a packing set to seal said stem; and
an actuating means connected to a second end of said stem, for driving it;
whereby said actuating means is able to be driven in a first sense to displace said stem, provoking a movement of said gate in a direction from said second end towards said first end of said flanged spool, and in a second sense, contrary to said first sense, for provoking a return movement of said gate.
A fourth aspect of the invention provides a stop means for halting displacement of a hollow device in an undersea pipe flow, said stop means comprising:
a flanged spool having a first flange able to be welded over an orifice drilled in an outer wall of a said flow pipe, at a point where said hollow device will operate, with an internal passage of said spool substantially in registration with said orifice;
a first gate valve having a first flange connected to a second flange of said flanged spool;
a second gate valve having a bonnet connected to a second flange of said first gate valve, said bonnet being provided with a stem and with a gate connected to a first end of said stem, said bonnet having a packing set to seal said stem; and
an actuating means connected to a second end of said stem, for driving it;
whereby said actuating means is able to be driven in a first sense, to displace said stem and to provoke a movement of said gate in a direction from said first flange of said flanged spool towards said second flange thereof, and is able to be driven in a second sense, contrary to said first sense, provoking a return movement of said gate.